There are different prior art systems for optical recording based on the forming of fluorescent compounds from non-fluorescent precursors, including the UV-light exposed compounds of bis-diarylchloromethyl-1,3,4-oxadiazoles which are disclosed in U.S. Pat. No. 3,869,363. Moreover, many other systems are described in Zweig “Photochemical Generation of Stable Fluorescent Compounds” in Pure and Applied Chemistry, Vol. 33, 389-410 (1973) herein incorporated by reference. The main disadvantage of systems using these compounds is the requirement to use lasers with wavelengths shorter than 500 nm for the reading of stored information in the system. Thus, these systems exclude the possible use of modern diode lasers with wavelengths over 600 nm for reading the information in the storage device.
Photochromic lactams of Rhodamine B and peri-phenoxy derivatives of polycyclic p-quinones are suggested for use in these memory devices in which the luminophores are photochemically generated (U.S. Provisional Patent Application No. 60/03258 filed on Dec. 10, 1996 and U.S. Provisional Patent Application No. 60/033709 filed on Dec. 20, 1996, herein incorporated by reference). These compounds can be used in optical memory devices employing modem diode lasers with the wavelengths over 600 nm for reading the stored information. However, photochromic systems based on the generation of luminescent products have the common disadvantage of the destruction of the photoinduced luminescent product during the reading process. Moreover, these systems have low light sensitivities which then requires high energy densities of irradiation during the recording process which can lead to destruction of the memory material.